Self Timer & Focusing Question

My fiance and I will be going on vacation soon and I plan on bringing my Nikon D3100 with the 18-55mm kit lens with me. My question is how do I properly focus the camera, set the self timer and jump in the picture? I did a little practice on this the other day and we weren't as focused as I'd like. (He was of course focused better than I was.) He is also about 8 inches taller than me. I was shooting in Aperture mode f4, AF-S, single point AF, self timer selected, I was focusing on his eye then doing a little recomposing so that I could fit in the picture, then fully pressing the shutter button and stepping into the picture. Is there a better way to do this? Any tips would be greatly appreciated!